Residual current circuit breaker

Residual current circuit breaker

Residual-current device ( RCCB , of English R esidual C urrent operated C ircuit- B reaker , mutatis mutandis, as a differential current circuit breaker hereinafter) are the most commonly used devices from the parent group of the fault current protective devices ( RCD from Engl. R esidual C current D evice ). In the older, colloquially still common terms FI-circuit breaker or FI-switch , "F" stands for the word error and "I" for the symbol of the electrical current strength . Due to the harmonization in standardization at international level, the term RCD has been used in general in German-language standards and literature since 2008 .

Residual current protective devices of all types switch off the voltage in the event of dangerously high residual currents to earth and thus contribute significantly to reducing life-threatening electrical accidents in low-voltage networks. They are connected upstream of the overcurrent protection devices in circuit distributors . There is also a combination in the form of the RCBO , which combines the function of the residual current device and the line circuit breaker in one device.

Basics

Protection goals

The electrotechnical standards define requirements for the protection of people and animals against electric shock . This is achieved through a combination of:

• Basic protection as a precaution against direct contact with active parts through basic insulation in a fault-free state,
• Fault protection in the event of indirect contact with accessible parts, for example the metallic housing of electrical equipment , which can become dangerous active parts in the event of a fault.

The use of residual current circuit breakers goes beyond basic and fault protection. In addition to fault protection and fire protection, it is primarily used as additional protection .

Extra protection

Time / current ranges for AC according to IEC / TS 60479-1 mod. with c ₁ as the flicker _threshold and trigger points of a residual current circuit breaker with I _Δn = 30 mA

A measure under certain conditions is called additional protection . This includes the residual current circuit breaker with its protective effect in the event of a simultaneous failure of the basic protection and the fault protection. This means that a double or even multiple fault occurs in the electrical system or electrical equipment. The residual current circuit breaker does not prevent electric shock and does not reduce the level of the residual current through the human body. Depending on the altitude, however, the duration of a flow through the body must be limited in such a way that the risk of ventricular fibrillation as an immediate life-threatening cardiac arrhythmia is reduced to a minimum. The maximum permissible rated _{residual current} I _Δn for personal protection is 30 mA. The use of the residual current circuit breaker as the sole protection against electric shock, i. H. without taking basic and error protection into account, is not permitted.

A residual current circuit breaker with a rated residual current not greater than 30 mA must be provided for:

• Sockets in final circuits with a rated current not greater than 32 A, which are intended for use by non-technical electrotechnical persons and for general use
• Final circuits for portable equipment used outdoors with a rated current not greater than 32 A.
• for lighting circuits (in Germany only in housing)

The need for a residual current circuit breaker as additional protection can be illustrated well in the following possible scenarios:

• careless handling or improper use of electrical equipment
• Toddlers
• Damage to the electrical system due to external influences
• Failure to comply with the five safety rules by qualified electricians
• Educational purposes
• Manipulation of an electrical system or electrical equipment by laypeople or unprofessional work by skilled workers.

Error protection

Error protection in the TT system

Residual current circuit breakers must be used for fault protection if the condition for automatic shutdown of the power supply with overcurrent protective devices in the event of a ground fault cannot be met. This is often the case when there is a TT system based on the type of earth connection . Due to the lack of an electrical connection between the system earth and the plant earth, the fault current is mainly limited by the propagation resistance of the system earth R _A. The following condition applies to personal protection:

${\displaystyle R_{\mathrm {A} }\leq {\frac {U_{\mathrm {T} }}{I_{\mathrm {\Delta n} }}}}$  With

R _A as the propagation resistance of the system earth including the protective conductor

U _T as contact voltage with a maximum of 50 V AC without time limit

I _Δn as the rated residual current of the residual current circuit breaker

Thus a maximum resistance to propagation would be possible of:

${\displaystyle R_{\mathrm {A} }={\frac {50\,\mathrm {V} }{30\,\mathrm {mA} }}\approx 1{,}67\,\mathrm {k\Omega } }$

Since in the event of a fault at the expansion resistance, approximately the entire phase conductor- earth voltage U ₀ drops from 230 V, the residual current is at least 4.6 times the rated residual current. This means that the required switch-off time of 0.2 s in the TT system is observed.

Residual current circuit breakers with a rated residual current greater than 30 mA may be used in the following cases:

• Distribution circuits
• Final circuits if this is necessary for reasons other than protection against electric shock.

Under the boundary condition of 4.6 times the rated residual current, the following propagation resistances would be possible depending on the respective residual current circuit breaker:

I Δn	10 mA	30 mA	100 mA	300 mA	500 mA	1 A
R A	5 kΩ	1.67 kΩ	500 Ω	167 Ω	100 Ω	50 Ω

Fire protection

To protect against electrically ignited fires, according to the VdS specifications, a fault current between the outer conductor and protective conductor or earth must not be greater than 420 mA. For this measure, residual current circuit breakers with a rated residual current of up to a maximum of 300 mA can be used. Depending on the rated residual current, the following heat outputs can occur at a fault location:

Rated residual current	Heat output at 230 V alternating voltage
030 mA	07 W
100 mA	23 W
300 mA	69 W

These thermal outputs are considerably lower than they would be with overcurrent protection devices alone. Separate arc fault protection devices are also available for fire protection , which must be installed in addition to the fault current circuit breaker and offer protection against cable fires , as can occur in the event of a cable break .

Working principle

Assemblies of a two-pole residual current circuit breaker 1:  switch lock ; 2: secondary winding; 3: Total current transformer toroidal core; 4: test button

Four-pole residual current circuit breaker on a three-phase connected consumer

Open four-pole residual current circuit breaker, summation current transformer with red-brown, thick working current windings, the secondary winding for the tripping mechanism (yellow) and the test current winding (blue)

The residual current circuit breaker trips at the latest when the rated residual current is reached and disconnects the affected circuit from the upstream network on all poles - including the neutral conductor with four-pole switches. The internal test circuit is also switched off because its current limiting resistor is not designed for continuous operation (incorrect operation). The protective conductor is not part of the residual current circuit breaker and is not switched off.

Fault currents occur when part of the current flows back to the power source via an undesired current path . Part of this current path can be the protective conductor , the housing of electrical equipment , the ground including all metallic structures in electrical contact with the ground and the body of a person or animal. The residual current circuit breaker forms the arithmetic sum of all instantaneous values ​​of the currents in the outer conductors and the neutral conductor. In a system without a ground fault, the sum is always zero.

The summation is done by a summation current transformer . Depending on the number of poles, two, three or four primary windings lead through it. They are designed in such a way that their induction effects cancel each other out in a fault-free state. No magnetic flux is generated in the converter core and therefore no voltage is induced in the secondary winding. If a fault current flows back to the current source via such an undesired current path, then the sum of all currents through the summation current transformer is no longer zero. This results in a magnetic flux in the converter core and induces a voltage in the secondary winding. The secondary current triggers a switch lock via the holding magnet release and switches off the circuit on all poles.

The summation current transformer works like a transformer and, like it, is also frequency-dependent. It can therefore only detect AC residual currents or pulsating DC residual currents. With smooth DC residual currents, there is no transmission, i.e. no induction in the secondary winding - the residual current is not detected. In the case of a mixed form (smooth DC residual current superimposed by AC residual current), the AC residual current can only be weakened or not transmitted at all, since the iron core is partially or completely premagnetized by the smooth DC residual current.

Universal current-sensitive RCDs (e.g. type B) sometimes have a second converter core for additional detection of smooth DC residual currents, which can be equipped with a Hall sensor to detect the magnetic field directly, and / or other electronics for e.g. frequency responses and to better record (or hide) their current dependencies and thus offer different types for the respective application purpose.

Summation current transformer

The summation current transformer contains a toroidal core , wound from crystalline or nanocrystalline soft magnetic tape. Ferrite cores are not suitable because of the insufficient permeability and saturation induction. In order to achieve the necessary power to trigger the residual current circuit breaker, toroidal cores with a certain size and mass are necessary, typical weight approx. 40 g. The cores are often encapsulated in an insulating manner, whereby no force may be exerted on the cores due to possible shrinkage of resins, since this changes the magnetic properties. Plastic troughs into which the cores are loosely placed are also common. Around the core (i.e. threaded through) 2 to 4 working current windings made of thick enamelled copper wire as well as the secondary winding and, if necessary, a test winding, each made of thin jumper wire.

Key switch

Functional principle of a holding magnet release

The switch lock is the mechanism that connects the manual operation (lever or trigger) and the trigger of the summation current transformer with the switching contacts. This is where the release spring is located, which is pre-tensioned when switching on (by hand) and provides the necessary force and speed for safe release. The mechanics for the trip-free release are also housed here. The pre-tensioned key switch can be triggered with minimal (practically no) effort and cannot be blocked from the outside.

The summation current transformer acts on the key switch, for example by means of a holding magnet release. It is fed by the secondary winding of the summation current transformer. A holding magnet release consists of a permanent magnet, two legs with a magnetic shunt and an armature made of soft magnetic material and an excitation winding. The magnetic flux of the permanent magnet leads over both legs and the armature. As a result, the armature is held against the spring force to the switching mechanism. If a current now flows in the field winding, a second magnetic flux is generated. In one half-wave the total flux increases and in the other half-wave it is weakened so that the spring pulls the armature from the pole faces of the two legs. The switch lock is triggered and the affected circuits are switched off.

Limits of the protective effect

The protective effect of a residual current circuit breaker does not occur in the following cases :

• A person touches active parts of different potential. These are two or more external conductors with different phases or one external conductor and the neutral conductor. In this case, the person is in a relatively good electrical insulating location from the earth and has no contact with earthed objects or the protective conductor.
• when a transformer (such as an isolating transformer ) breaks the circuit and a person on the secondary side touches both poles at the same time
• If an overcurrent occurs as an overload or short circuit , protection can only be ensured by automatically switching off the power supply using an overcurrent protection device
• a conductor short-circuit is not detected because no fault current flows to earth
• Depending on the type of fault current, there is a risk that a fault current circuit breaker will not respond. It does not have the ability to record all types of current (especially direct current).
• A type B + residual current circuit breaker  for enhanced preventive fire protection detects residual currents with frequencies of up to 20 kHz only to earth. An arc fault protection device would also be required to detect such an interference current between two active conductors .

Classification according to the type of fault current form

Residual current forms and residual current circuit breakers suitable for their detection according to type

Residual current circuit breakers are divided into types according to the type of residual current they can detect. A distinction is made between type AC, type A, type F and type B / B + in ascending order of sensitivity.

1. Type AC  : 

   For the detection of purely sinusoidal AC residual currents that can occur suddenly or increase slowly. The function is ensured if a smooth DC residual current does not exceed the value of 6 mA. (No longer permitted in Germany)

2. Type A  : 

   In addition to the functionality of the AC type, pulsating DC residual currents are recorded. Type A is the most commonly used residual current circuit breaker for common applications.

3. Type F  :  

   In addition to the functionality of type A, a mixture of fault currents of different frequencies up to 1 kHz is recorded. Such residual currents can occur in single-phase electrical equipment with frequency converters (e.g. washing machines). The function is ensured if a smooth DC residual current does not exceed the value of 10 mA.

4. Type B  :   

   In addition to the functionality of type F, smooth DC residual currents are recorded. The function is ensured if different types of residual current overlap, regardless of:

   • Leading edge angle
   • polarity
   • occurring suddenly or slowly increasing

   Type B is also called universal current sensitive .

5. Type B +  :     

   In addition to the functionality of type B, sinusoidal AC residual currents are recorded for frequencies up to 20 kHz. Type B + is therefore used for preventive, enhanced fire protection .

Combined types RCD / LS and RCD socket

There are also combined RCDs with miniature circuit breakers (LS) (e.g .: 30 mA RCD and 13 A miniature circuit breaker), which are called RCBO (colloquially "FI / LS"). An RCBO with the number of poles 1P + N typically has the same installation width (or the same number of modules , abbreviation TE) as a two-pole miniature circuit breaker or a two-pole FI circuit breaker (two TE).

In order to protect individual sockets with RCD, RCD sockets (SRCD) (colloquially "FI sockets") are also available. However, these only represent additional protection and do not replace a conventional RCD according to DIN EN 61008-1 (VDE 0664-10), where this is required.

Characteristic values

Rated residual current

The most important characteristic value is the rated residual current I _Δn , at which a residual current circuit breaker must trip at the latest. The values ​​for I _Δn are 10 mA, 30 mA, 100 mA, 300 mA, 500 mA and 1 A. In practice, a purely sinusoidal alternating _{fault current} between 0.6 ·  I _Δn and 0.8 ·  I _{Δn is triggered} .

Non-tripping fault current

The non-tripping _{fault current} I _Δn0 is 0.5 ·  I _Δn for a purely sinusoidal _{AC fault current} . A residual current circuit breaker may only trip above half the rated residual current.

Trip areas, fault current forms

In addition to the pure AC residual current, there are other types of residual currents for which the following tripping ranges are defined:

• 0.35 ·  I _Δn to 1.4 ·  I _Δn for pulsating direct currents
• 0.25 ·  I _Δn to 1.4 ·  I _Δn for cut half waves with a phase _{cutting angle} of 90 °
• 0.11 ·  I _Δn to 1.4 ·  I _Δn for cut half waves with a phase _{cutting angle} of 135 °
• up to 1.4 ·  I _Δn for pulsating direct currents superimposed with a smooth direct current of maximum 6 mA
• 0.5 ·  I _Δn to 1.4 ·  I _Δn for mixed frequency _currents
• 0.5 ·  I _Δn to 2 ·  I _Δn for smooth direct currents

Rated current

The rated current I _n is a fixed value that can be permanently carried by a residual current circuit breaker for each outer conductor. Preferred values ​​for I _n are 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 63 A, 80 A, 100 A and 125 A.

Shutdown time

• For residual current circuit breakers without a time delay, the maximum permissible disconnection _{times are} 0.3 s for a current of I _Δn , 0.15 s for 2 ·  I _Δn and 0.04 s for 5 ·  I _Δn . This makes the triggering of (fatal) ventricular fibrillation very unlikely, but it cannot be completely ruled out. a. because the physiological effect of a current pulse depends on the phase of the heartbeat in which it falls.
• For selective residual current circuit breakers - _i.e. with a time delay - the maximum permissible disconnection _{times are} 0.5 s for a current of I _Δn , 0.2 s for 2 ·  I _Δn and 0.15 s for 5 ·  I _Δn .

Non-trip time

Non-tripping times are only defined for selective residual current circuit breakers. The shortest non-tripping _times are 0.13 s for a current of I _Δn , 0.06 s for 2 ·  I _Δn and 0.05 s for 5 ·  I _Δn .

Contact sequence

Play media file

Contact sequence of a 4-pole residual current circuit breaker

The moving contacts and their mechanical coupling of a multi-pole residual current circuit breaker are designed in such a way that the contacts of the three outer conductors close or open at the same time as possible. The contact of the neutral conductor must not close or open before that for the outer conductor. Otherwise, during the switching process of a 4-pole residual current circuit breaker in the assigned final circuits, an asymmetry could result in a neutral point shift and damage the connected electrical equipment.

selectivity

Example of the selectivity of residual current circuit breakers

In order to achieve selectivity , residual current circuit breakers can be connected in series. Only the fault current circuit breaker directly assigned to the faulty circuit should trigger without a time delay . This protective device is also preceded by a residual current circuit breaker with a time delay and is marked with the symbol for selectivity. There is selectivity if:

• the shortest non-tripping time of the upstream residual current circuit breaker with time delay is higher than the highest disconnection time of the downstream residual current circuit breaker without time delay
• the rated residual current of the upstream residual current circuit breaker with time delay is at least three times the value of a downstream residual current circuit breaker without time delay (total selectivity)

Residual current circuit breakers with time delay are often referred to as selective or time-delayed residual current circuit breakers . As with overcurrent protective devices , the aim is to achieve higher availability of the electrical system through selectivity. Also note:

• Residual current circuit breakers with time delay cannot be used to provide additional protection , as the rated residual current is at least 100 mA. The current-time characteristic curve for the highest switch-off time is always in a range in which there is a risk of ventricular fibrillation .
• The downstream residual current circuit breaker must not have any higher sensitivity than the upstream residual current circuit breaker (detection according to the type of residual current). A type B residual current circuit breaker, for example, must not be connected downstream of a type A.

Interference immunity

Residual current circuit breakers with short-time delay are used to prevent unwanted tripping . Causes for unwanted tripping can be:

• Overvoltages due to switching operations and atmospheric effects
• Compensation processes after the connection or a load change of capacitive or inductive operating equipment

The maximum permissible switch-off times are the same as those of residual current circuit breakers without a time delay. The labeling is manufacturer-specific, for example from:

• ABB with the indication AP-R and the use of the term short- term delayed
• Siemens with the symbol and the use of the terms super-resistant or short- term delayed

The use of residual current circuit breakers with time delay (selectivity) is also possible if the additional protection measure can be dispensed with.

Designations, definition of terms

The following terms were previously used in German standards:

• Residual current circuit breaker (FI) for devices independent of the mains voltage (without auxiliary voltage source),
• Residual current circuit breaker (DI) for mains voltage-dependent devices (with auxiliary voltage source).

You can also find:

• Personal protection machine is a marketing name and technically not precisely defined.
• Personal protection switch is a designation that is used for residual current circuit breakers in supply lines and extensions as well as in adapter plugs and is otherwise not precisely defined. The BGI608 specifies requirements for such portable protective devices when used as a feed point for so-called small construction sites .

The following designations were used for residual current circuit breakers combined with line circuit breakers:

• FI / LS circuit breakers , if they were independent of the mains voltage,
• DI / LS circuit breakers if they were dependent on the mains voltage.

The distinction into grid-voltage un -dependent and line-voltage-dependent protective equipment is not made in English language standards and not used in the IEC and EN standards. The following terms are used in the international device standards:

• RCCB = Residual Current operated Circuit-Breaker without overcurrent protection, corresponds to the pure FI or DI switches, (is equivalent to RCD residual-current device)
• RCBO = Residual Current operated circuit breaker with integral over current protection, corresponds to the combined FI / LS and LS / DI switches
• SRCD = Socket outlet Residual Current Device, are FI or DI sockets (to increase the protection level, mostly in electrical installations with classic zeroing in socket form)
• PRCD = Portable Residual Current Operated Device, are portable, most commonly found under personal protection adapters
• RCU = Residual Current Units, are residual current releases for attachment to miniature circuit breakers

Opened GFCI from a socket

• CBR = Circuit-Breaker incorporating residual current protection, are circuit breakers with residual current protection function
• GFCI = Ground Fault Circuit Interrupter, is the term used in North America for RCCB

In the installation regulations for electrical systems, residual current circuit breakers are consistently listed under the umbrella term RCD. A differentiation between FI, DI or special designs is no longer made in the installation regulations for electrical systems. The protection goal is decisive here. This must be implemented with different designs depending on the place of use.

Regulations

The use of residual current circuit breakers is mandatory in many countries for new installations or changes in the household and industrial sector, at least for sockets (up to 20 A or 32 A) (e.g. DIN VDE or ÖVE) in addition to the installed overcurrent protection devices. A residual current circuit breaker with a tripping current difference of 300 mA is often prescribed by some energy supply companies as fire protection for the entire electrical system if the building is not fed via underground cables , but via roof overhead lines .

Mains-voltage are in Europe, except for Britain, un -related fault circuit interrupter (RCD) prescribed. The underlying safety philosophy calls into question the reliability of the electronic amplifier circuits, which are used in the simpler and smaller electronic DI switches (residual current circuit breakers) in English-speaking countries.

Germany

In Germany, residual current circuit breakers in new buildings have been required since May 1984 for rooms with a bathtub or shower in accordance with DIN VDE 0100-701 (the only exception: permanently connected water heaters).

Since June 2007 all new buildings also all outlets - circuits which are intended for use by laymen and for general use, be equipped with a residual current device with a rated residual current not exceeding 30 mA. This applied to final circuits with a rated current of up to 20 A indoors and up to 32  A outdoors (DIN VDE 0100-410: 2007-06, section 411.3.3, transition period until January 2009).

Since October 2018, these requirements also apply indoors for socket outlet circuits up to 32 A, as well as for lighting circuits in apartments (DIN VDE 0100-410: 2018-10, section 411.3.3, transition period until July 2020).

For halls and There is also a requirement for residual current circuit breakers for outdoor pools and for rooms and cabins with sauna heaters. The term "damp room", which is often misunderstood, does not refer to bathrooms or toilets in living spaces. According to the definition in DIN 68800, it is a damp room if the humidity is above 70% for a long time. In DIN VDE 0100-200: 2008-06 Section NC.3.3, kitchens in apartments and bathrooms in apartments and hotels are explicitly classified as dry rooms with regard to installation (since moisture only occurs temporarily in these rooms).

There is no obligation to retrofit old systems. This means that a system can continue to be operated if the system complied with the standards and guidelines applicable at the time and still complies with them today.

In Germany, however, retrofitting a residual current circuit breaker is unavoidable under the following circumstances:

• when changes in use are made
• in the case of extensions of use, conversion measures or renovations that affect the substance
• if new legal ordinances that require retrofitting come into force ( note TAB )
• after expired transition periods
• in the event of immediate danger to people and property

Note: The mere replacement of equipment, e.g. a socket, does not require adaptation to new standards. However, if the socket is moved to another location or a socket circuit is expanded to include another socket, then at least this circuit must be adapted to the current state of the art (standards).

Residual current circuit breakers must also be used in agriculture, especially when keeping animals. The reduction of the permanently permissible contact voltage to 25 V alternating voltage and 60 V direct voltage is no longer required in accordance with DIN VDE 0100-705: 2007-10.

Austria

A residual current circuit breaker has been a legal requirement in Austria since 1980. According to ÖVE E8001-1 / A1: 2013-11-01 residual current circuit breakers with a nominal residual current of max. 30 mA prescribed for all circuits in which there are sockets and whose nominal current does not exceed 16 A.

The use of type AC is not generally prohibited. In most cases (threatened damage in the event of a power failure), a type G FI switch must be used, which is briefly delayed and surge-proof. A back-up fuse with the rated current of the FI switch is only permitted if this is explicitly stated by the manufacturer, otherwise a 40 A FI switch must be protected with a maximum of 25 A, for example. Due to these special features, several manufacturers sell Austria-specific (and significantly more expensive) variants of their products, which are referred to , for example, as short-term delayed , type G , pre-fuse-proof or with rated current pre-fuse .

On construction sites, all socket circuits with a rated current of up to 32 A and in agricultural and horticultural facilities (not in the adjacent residential buildings), in sauna areas, in swimming pools, in outdoor swimming pools, in experiment stands in classrooms , in rooms used for medical purposes, in bathrooms, Provide additional protection on campsites, on boat docks and in wall lights in the hand area of ​​changing rooms regardless of their rated current .

Switzerland

In Switzerland , according to the Low Voltage Installation Standard (NIN) 2005 4.7.2.3.1-8, max. 30 mA prescribed for baths and shower rooms, outdoor sockets, damp and wet rooms, corrosive environments and explosive atmospheres , construction sites, exhibition grounds, fairs, fairgrounds, electr. Experimental arrangements. (all sockets ≤ 32 A).

300 mA are prescribed for installations in corrosive environments, areas with a risk of explosion and fire as well as in agricultural operations for the entire installation, whereby in agriculture all plug-in devices must be equipped with 30 mA residual current circuit breakers.

On January 1, 2010, the new NIN 2010 came into force. From now on, every freely accessible socket must be ≤ 32 A with a max. 30 mA residual current circuit breaker must be protected. Exceptions are, for example: Sockets in IT systems, where operational safety is more important and the room with access control can only be entered by an instructed group of people.

In residential construction, type A is generally used for all applications.

To check the permissible switch-off time in the installation, the following applies for circuits ≤ 32 A 0.4 s. The test with half and the full differential current with a tripping time of <0.3 s is purely a device test and has no significance for the proof of safety for electrical installations (SiNa).

Application area

In the power distribution panel ( sub-distribution, fuse box ) installed residual-current device

Residual current circuit breakers can be used in all AC systems ( TN , TT and IT systems ). In the TN system it is mainly the additional protection. The fault protection is already fulfilled by overcurrent protective devices. In the TT system, the residual current circuit breaker often provides fault protection, as the triggering of overcurrent protective devices is not guaranteed. Use should be the exception in the IT system. A separate residual current circuit breaker is required for each piece of electrical equipment.

In the new building sector, nothing speaks against securing the entire power supply. For this purpose, at least 2 RCDs must be installed in an apartment sub-distributor so that the entire system is not switched off in the event of a fault. This can be a hindrance under certain circumstances, so that one should limit the circuits protected by the residual current circuit breaker. When making the selection, leakage currents from electronic loads (e.g. electronic ballast ) or their possible type of residual current (e.g. built-in frequency converter in washing machine ) must also be taken into account. When retrofitting old apartments, the residual current circuit breaker often triggers incorrectly, the cause of which is sometimes difficult to isolate. The cause is often incorrect wiring, in which, for example, in sockets or water heaters, current flows through the protective conductor instead of the neutral conductor.

Disconnections by residual current circuit breakers can also be caused by external events, for example by overvoltage pulses caused by lightning strikes in overhead lines. This can often lead to unpleasant side effects, such as switching off heating or cooling systems, although there is no fault in your own system. For this reason, circuit breakers have also been developed which automatically switch on the voltage again two or three times after being triggered. Only if the error persists will they be permanently switched off. These models are of particular interest for remote-controlled systems where there is no staff on site who could switch the circuit breaker on again.

System faults can be found more quickly if the neutral conductors of all final circuits are routed via isolating terminals or 2 or 4-pole miniature circuit breakers are generally used that also switch the neutral conductor for each final circuit; Such miniature circuit breakers are designated with “1p + N” or “3p + N”, and the contact for the neutral conductor is opened with a lag and closed with a lead.

Check the residual current circuit breaker

Test button with resistance

Measuring device for testing RCDs according to DIN VDE 0100-600

Test button

There is a test button (T) on the residual current circuit breaker with which the function of the device can be tested. A current path leads from an external conductor past the summation current transformer to the neutral conductor. The test button and a resistor that determines the level of the differential current are located in this current path. A residual current is simulated when the test button is pressed. The button closes the current path via the resistor. This creates a differential current that exceeds the response value of the residual current circuit breaker and triggers the RCD. However, the function test using the test button does not provide any information about the correct condition of the tracked circuit.

Manufacturers recommend an inspection by the user at least every six months. It is often suggested that the days of the time change should be used as a reminder. According to DGUV regulation 3), shorter time intervals may also be required.

Determination of the tripping fault current

The tripping residual current (response value of the residual current circuit breaker) must be between 50% and 100% of the rated residual current. In practice the value is around 70%.

RCD test according to DIN VDE 0100-600 (VDE 0100-600): 2017-06

According to DIN VDE 0100-600, the effectiveness of the protective measure "Automatic shutdown of the power supply" in the electrical installation including determination of the characteristic values ​​of the residual current circuit breaker must be proven with suitable test devices according to IEC 60364-6 (modified; for Germany: DIN VDE 0100-600). The corresponding requirements according to DIN VDE 0100-410 must be observed.

The maximum switch-off time according to DIN VDE 0100-410 for socket outlet circuits up to and including 63 A in TN systems is 0.4 s (at 230 V to earth, in the TT system 0.2 s). In practice, this value is around 20–40 ms. According to the building standard (DIN EN 61008-1, VDE 0664-10), the switch-off time for the device itself is 0.3 s for a full I _Δn , 0.15 s for 2  I _Δn and 0.04 s for 5  I _Δn .

In addition, the contact voltage and the earthing resistance are measured; these must not exceed the values ​​specified in the standard. The effectiveness of the automatic shutdown of the power supply by residual current protective devices (RCDs) must be checked with suitable measuring devices in accordance with DIN EN 61557-6 (VDE0413-6). The measured values ​​must be documented in suitable test reports; this can be a ZVEH test report, for example .

RCD test type A (Switzerland)

A qualified electrician always switches the switch off with the test button. Then a current of the magnitude of the nominal residual current is simulated and the residual current circuit breaker must trip within 0.4 s according to NIN 2010 chapter 4.1. There are small hand testers and installation testers on the market that enable this test from the outer conductor to the protective conductor. The tripping time is recorded in the safety certificate, with a 30 mA RCD this is 20 to 30 ms in practice. Short-time delayed residual current circuit breakers require 40 to 100 ms.

Selective residual current circuit breakers with 300 mA for fire and corrosion protection trigger with the pulse method (50% and 100% residual current) approximately in 200 to 400 ms, the standard (NIN 6.1.3.9 / EN 61008-1) requires 130 to 500 ms .

Historical and development

Spider web FID 25/4

The residual current circuit breaker was patented by Schuckert as early as 1903 under the name of summation current circuit for earth fault detection ( DRP no. 160.069). At AEG, Kuhlmann describes a method for measuring earth fault currents in the Berlin network. The technology on which today's residual current circuit breakers are based is further developed by Nicholsen (1908, USA Pat. No. 959.787).

At the beginning of the 1950s, after countless suggestions and technical studies on the basic applicability of the circuit as a protective device, a sophisticated residual current circuit breaker for widespread use by electricity customers was presented for the first time. A residual current circuit breaker from the company Schutzapparate-Gesellschaft & Co. mbH is documented for 1951 . KG, Schalksmühle / Westf. (Schupa) with the trade name Spinnennetz , which was designed in two-, three- and four-pole versions for a rated current of 25 A and voltages up to 380 V with a tripping fault current of 0.3 A. A lower trigger threshold was discussed, but rejected as economically unreasonable. The leakage currents permitted at the time for heating devices would have led to frequent false trips if the trip threshold had been lower.

In 1957, Gottfried Biegelmeier developed a residual current circuit breaker at Felten & Guilleaume in Austria . These were legally prescribed in Austria in 1980 in private households, whereby the tripping current was gradually reduced from the original 100 mA to 70, 65 and 30 mA. Since the beginning of 1985, with the entry into force of regulation SEV 1000-1.1985, this has also been applicable in Switzerland.

Similar facilities

• Protective line system  - an insulation testing device in special facilities
• PRCD  - A mobile residual current protective device that is switched into the supply line of devices
• Residual Current Monitor (RCM) - device for monitoring and displaying residual / differential currents
• Arc fault protection device  - A device that detects and switches off arcing faults to earth or between conductors is also manufactured in combination with residual current circuit breakers

Norms

• DIN EN 61008-1 ( VDE 0664-10): 2015-11 Residual current / residual current circuit breakers without built-in overcurrent protection (RCCBs) for house installations and for similar applications - Part 1: General requirements
• DIN EN 61009-1 (VDE 0664-20): 2015-11 Residual current / residual current circuit breakers with built-in overcurrent protection (RCBOs) for house installations and for similar applications - Part 1: General requirements
• DIN EN 62423 (VDE 0664-40): 2013-08 Residual current / residual current circuit breaker type F and type B with and without built-in overcurrent protection for house installations and for similar applications
• DIN VDE 0100-100: 2009-06 Installation of low-voltage systems - Part 1: General principles, provisions of general characteristics, terms
• DIN VDE 0100-410: 2018-10 Construction of low-voltage systems - Part 4-41: Protective measures - Protection against electric shock
• DIN VDE 0100-530: 2018-06 Installation of low-voltage systems - Part 530: Selection and installation of electrical equipment - switching and control devices
• DIN VDE 0100-600: 2017-06 Erection of low-voltage systems - Part 6: Tests
• DIN VDE 0100-701: 2008-10 Erection of low-voltage systems - Part 7-701: Requirements for production facilities, rooms and special types of systems - rooms with bathtub or shower
• DIN VDE 0100-705: 2007-10 Erection of low-voltage systems - Part 7-705: Requirements for production sites, rooms and special types of systems - Electrical systems for agricultural and horticultural production sites
• DIN EN 61557-6 (VDE 0413-6): 2008-05 Electrical safety in low voltage networks up to AC 1 000 V and DC 1 500 V - Devices for testing, measuring or monitoring protective measures - Part 6: Effectiveness of residual current protective devices (RCD ) in TT, TN and IT systems
• ÖVE E8001-1 / A1: 2013-11-01 Installation of electrical systems with nominal voltages up to AC 1000 V and DC 1500 V, Part 1: Terms and protection against electric shock (protective measures)

literature

• NIN2005 4.7.2.3 /4.1.2.5.
• A. Senner: Electrical engineering. 4th edition. Verlag Europa - Lehrmittel, 1965.
• Ernst Hörnemann, Heinrich Hübscher: Electrical engineering specialist training in industrial electronics. 1st edition. Westermann Schulbuchverlag, Braunschweig 1998, ISBN 3-14-221730-4 .
• Günter Springer: Expertise in electrical engineering. 18th edition. Verlag Europa - Lehrmittel, Wuppertal 1989, ISBN 3-8085-3018-9 .
• M. Kampler, H. Nienhaus, D. Vogt: commissioning testing of low voltage (=  VDE publications . No. 63 ). 3. Edition. VDE Verlag, Berlin / Offenbach 2008, ISBN 978-3-8007-3112-1 , p. 127 ff .

Web links

Commons : Residual Current Circuit Breaker  - Collection of pictures, videos and audio files

Wiktionary: Residual current circuit breaker  - explanations of meanings, word origin, synonyms, translations

• Simple representation of the functionality of a residual current circuit breaker
• Residual current protective devices - technology primer. , Edition 02/2018 (PDF; 3.3 MB) Siemens AG
• Technical manual - Basics of protection. (PDF; 3.9 MB) Hager Switzerland
• Residual current circuit breaker - technical data. (PDF; 1.1 MB) FIG
• General brochure RCCB. (PDF; 4.7 MB) Doepke

Individual evidence

1. ↑ IEC 60050: 442-05-02 "Residual current protective device". In: IEV , International Electrotechnical Dictionary. DKE, accessed on February 6, 2017 . 
2. ↑ Netzikon
3. ↑ Residual current protective devices (RCDs). Determination of a uniform designation by Committee K 221. (No longer available online.) DKE VDE, November 6, 2008, archived from the original on September 3, 2012 ; Retrieved July 17, 2012 . 
4. ↑ Low- interference electrical installation. (PDF; 367 kB) Guidelines for damage prevention. In: VDS 2349. VdS Verlag, February 2000, accessed on May 3, 2012 . 
5. ↑ Hager company publication, page 13, accessed on October 29, 2018
6. ↑ VDE 0160; EN 50178 chapter 5.2.11.
7. ↑ https://www.vacuumschmelze.de/fileadmin/docroot/medialib/documents/produkte/kb/FIKerne_dt.pdf toroidal cores for FI circuit breakers, company publication of VACUUMSCHMELZE GmbH & Co. KG, accessed on October 29, 2018
8. ^ Paul Heymann (ed.): Expertise in electrical professions . Bildungsverlag EINS, Torisdorf 2009, ISBN 978-3-8242-4290-0 .
9. ↑ Günter Grünebast: Actual load capacity of RCDs. (PDF) In: Praxisprobleme. www.elektro.net, accessed on August 3, 2016 . 
10. ↑ Selection and operation of electrical systems and equipment on construction and assembly sites. Professional association information for safety and health at work. BGI 608.
11. ↑ "Fixed residual current protective devices (SRCDs) for increasing the protection level" according to E DIN VDE 0662 and as additional protection according to DIN VDE 0664-50.
12. ^ Western Automation - Research & Development , accessed July 23, 2010.
13. ↑ As a rule, old systems are protected. Old systems are systems that at the time of their construction complied with the regulations applicable at the time.
14. ↑ A final circuit is a circuit to which power consumption devices or sockets are directly connected. (PDF; 129 kB) Explanation of terms; State Environment Agency North Rhine-Westphalia; Retrieved March 1, 2012.
15. ↑ Werner Hörmann, Bernd Schröder, Burkhard Schulze: VDE series 67a; "Setting up low-voltage systems in rooms with bathtubs or showers", comment from DIN VDE 0100-701: 2008-10 . 3. Edition. VDE Verlag GmbH, Berlin and Offenbach 2010, ISBN 978-3-8007-3134-3 , p. 189 ff .
16. ↑ According to DIN 18015-2 (applies to residential complexes in Germany), the allocation to residual current circuit breakers must be carried out in such a way that switching off a residual current circuit breaker does not lead to the failure of all circuits.
17. ↑ Schrack: PDF ( Memento of the original from March 9, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed January 31, 2012. 
18. ↑ DGUV regulation 3 (formerly BGV A3). (PDF) Electrical systems and equipment. (No longer available online.) DGUV, archived from the original on December 20, 2013 ; accessed on May 8, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
19. ↑ David Keller, Pius Nauer: NIN Know-how 67. (PDF; 262 kB) Questions and answers about NIN. (No longer available online.) In: Elektrotechnik 5/11. AZ Fachverlage AG, archived from the original on March 12, 2014 ; Retrieved May 9, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
20. ↑ Walter Schossig: History of protection and control technology. Lecture on the occasion of the International ETG Congress 2001 in Nuremberg.
21. ↑ Walter Schossig: The History of Electricity ( Memento from December 13, 2017 in the Internet Archive ) (PDF; 227 kB). In: VDI-Nachrichten . 1/2008. (P. 22 ff.).
22. ↑ HF Schwenkhagen : The residual current protective circuit, a new form of protective earthing. In: Elektro-Anzeiger magazine for the entire electrical and broadcasting industry . Edition 51/52 of December 29, 1951, (p. 488 ff.).
23. ↑ German Trademark Register No. 730393 , accessed on October 7, 2013.